Heretofore, it has, for the most part, been the practice in the liquid clarifying art to provide large diameter outdoor processing apparatus that make use of mechanically driven elements, such as rakes, or other driven elements, such as vibrated plates or rotating stirrers. One type of apparatus is called a "lamella" thickener and employs a pack of downwardly declining stacked metal or plastic trays, which may be vibrated for treating the sticky sludges, with bottom entry and top outflow, see pages 384 and 385 of the text "Mineral Processing Technology", by B. A. Wills, First Edition, 1979, published by Pergamon Press, Inc., Maxwell House, Fairview Park, Elmsford, N.Y. 10523. Equipment using rotating stirring is represented by the Emmett, Jr. U.S. Pat. No. 4,055,494 of 1977 and the Elie Condolios U.S. Pat. No. 4,260,488 of 1981. The former shows in FIG. 2, the use of an upwardly positioned impeller 49 and a series of downwardly spaced-apart mixing blades 69 mounted on a common drive shaft, while the latter patent shows a perforated, vertically spaced-apart group of paddle-like blades 7, and a lower pair of so-called conical blades 12 and 12, on a single motor driven vertical shaft 8 and finally, a horizontally extending material-compressing motor-driven screw 13.
The Pinto U.S. Pat. No. 4,192,752 of 1980 deals with a so-called clarifier for sugar juice which, as shown in FIG. 2, employs a group of downwardly-inwardly spaced, horizontally-extending, side-positioned trays 5, a rotary scraper 9, and a mud stirrer 17. A flocculation apparatus of Wilson U.S. Pat. No. 3,933,642 of 1976 appears to show an arrangement in which the liquid to be treated is introduced at the bottom end, see arrow 33, of a spiraled pipe coil unit made up of continuous pipe convolutions of upwardly increasing diameters and increasing lengths (see FIGS. 1 and 5). Its outlet 14 (see FIG. 3) is located at the upper end of the unit. It poses a highly complex and expensive manufacturing and replacement problem from the standpoint of the continuous length of the upwardly enlarged and lengthened pipe length portions, requires a powerful pumping action as to the sludge being treated, and presents a clogging and cleaning maintenance problem for clean-out. I have been unable to find any commercial installation involving this construction. The arrows of FIG. 3 appear to indicate that the liquid leaving the upper outlet end 14 of the pipe coil travels downwardly along an outer coil positioned and enclosed space and then moves upwardly along an inner chamber (see arrows 47 and 53 of the Figure). He relies on the use of so-called velocity gradients and centrifugal force in attempting to remove contaminating particles.